Lightweight and modular design of a hydraulically actuated quadruped robot with high payload-to-mass ratio

Abstract

Load-carrying horses, climbing mountain goats, and galloping cheetahs all exhibit impressive locomotion abilities, prompting the development of quadruped robots. Among different types of quadruped robots, hydraulically actuated robots have been widely concerned with their higher speed limit and load-bearing capacity. However, hydraulic quadruped robots usually comprise numerous components and high-pressure pipes, posing challenges to the design and component layout of the robots. To tackle these problems, this paper proposes a modular design method for the Spurlos quadruped robot. Based on the design goals and required functional composition, the robot is divided into four main parts: limb leg unit, torso, onboard hydraulic system, and control hardware. The critical issues of each part are solved correspondingly, including customized lightweight actuators based on multi-material design, active joint kinematics, lightweight torso structure with mortise and tenon joint, required flow rate estimation, and reliable hardware with hierarchical control strategy. Comparison with other advanced hydraulic quadruped robots indicates that the payload-to-mass ratio of the Spurlos robot adopting modular and lightweight design is superior to those based on other design principles. The design effectiveness and dynamic performance are validated through air walking, weight-bearing squat, and trotting experiments. The results demonstrate the robot’s good load-bearing capacity and locomotion abilities. The modular and lightweight structure design approach proposed in this study provide valuable reference for the structural design of other legged robots.